Performance Analysis of Collaborative Hybrid-ARQ Protocols over Fading Channels

Collaborative communications is a promising paradigm for future communications systems. In order to increase the spectral efficiency of collaborative schemes, an adaptive approach that prescribes the use of cooperation only upon erroneous reception of the transmitted packet by the destination has been recently proposed. This technique can be considered as a generalization of ARQ protocols to a collaborative scenario. In this paper, a performance analysis is presented for both Collaborative Hybrid-ARQ Type I (i.e., without memory) and Chase Combining (i.e., with memory). In particular, a closed form expression for the average number of retransmissions and throughput is derived for single-relay case. Morever, numerical results are presented in order to corroborate the analysis and get insight into the performance of the considered schemes.